DE-A-37 02 841 discloses a granulating device in which the drive motor for the shaft of the cutting knives and its housing are attached to a bearing plate supported by adjustable helical springs, which in addition to an elastic mounting of the bearing plate, also permits a specific change in its position when the cutting unit is in a suspended position.
The construction has the disadvantage that a relatively large lateral or vertical displacement occurs in the region of the elastic support even for a small displacement of the granulating head caused, for example, by heat expansion, due to the overall length of the bearing plate. Consequently, a uniformly accurate guidance of the cutting knives relative to the die plate is not obtained.
In order to achieve a uniform cutting action at the surface of the die plate by the cutting knives in the granulating device, a precise perpendicular placement of the shaft of the cutting knives with respect to the front surface of the die plate is necessary. One difficulty imposed by this requirement is that the die plate is not fixed but undergoes displacement at the beginning and during the granulation operating due to temperature changes.
Furthermore, an accurately-reproducible central positioning of the cutting knives relative to the die plate is of considerable importance in that this same initial position of the cutting knives is again established after an interruption in operation. Only, as long as these requirements are fulfilled, can there be a continuous production of objection-free strands or strings of plastic material and granulates of uniform quality.